This invention relates to aircraft navigation instruments; and more particularly, it relates to instruments which measure an aircraft's attitude in terms of roll, pitch, and heading.
In the prior art, the instruments which measure an aircraft's roll, pitch and heading have operated on inertial navigation principles. These inertial navigation instruments include three wide angle gyroscopes, and the reactions of the gyroscopes along three axes to the aircraft's movements are measured and translated into roll, pitch, and heading. An example of such an instrument is the LN-100 strap down initial navigation system by Litton Corporation.
A major drawback, however, of the above-described inertial navigation instruments is that they are too expensive to be practicable for use in many kinds of aircraft. Just the three wide angle gyroscopes, by themselves, cost about fifty-sixty thousand dollars. Consequently, in low cost drones that are shot down by the military as targets and in low cost private airplanes, inertial navigation instruments have found very little use.
Another prior instrument for measuring an aircraft's roll, pitch, and heading which operates on a different principle is disclosed is U.S. Pat. No. 5,101,356. Basically, that instrument operates on the principle of an interferometer wherein roll, pitch, and heading are measured by comparing the phases of three radio signals from three GPS receivers that are included in the instrument.
However, in the patent '356 instrument, the three GPS receivers must be separated from each other on the aircraft by as large a distance as possible (e.g.--they are located on the aircraft's nose, tail, and wing). At the same time, the three GPS receives must not move relative to each other. If both constraints are not met, the instrument will give erroneous results. But, in many cases both constraints cannot be met since an aircraft's wings generally will bend or flex during flight.
Accordingly, a primary object of the invention is to provide a novel structure for an instrument which measures the roll, pitch, and heading of an aircraft such that all of the above problems are overcome.